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How to delete/remove an element just by its x:Name?

    Question

  • Now, maybe I just know one element's x:Name, but I don't know its parent node.

    Is it possible to delete/remove this element? Or must I try to get its parent first?

    Friday, October 31, 2008 5:14 AM

Answers

  • I see - sounds like a cool project!

    In your example your animation is added to the Triggers collection for the rootElement so you can use something like:

    this.rootElement.Triggers.Remove(this.myAnimation);

    This would remove the trigger for the animation but not the element it is animation on, nor would it stop the animation.  So stop the animation first, remove the element, then remove the trigger.

    Monday, November 03, 2008 3:46 AM

All replies

  • With this Xaml:

     

     <Grid x:Name="LayoutRoot" Background="White">
            <StackPanel >
                <Button Content="Button1"></Button>
                <Button Content="Button2" Click="Button_Click"></Button>
            </StackPanel>
        </Grid>

     You could do this:

          private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                Panel element = button.Parent as Panel;
                element.Children.Remove(button);
            }

    This will work fine for things that derive from Panel: Grid, StackPanel, Canvas etc.

    If your element is in something else such as a Border which derives from UIElement and then defines it's own child property you would need to do this:

         private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                Border element = button.Parent as Border;
                element.Child = null;
            }


    So depending on how complex your xaml is you may need some conditional logic such as:

          private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                UIElement element = button.Parent as UIElement;
                if (element is Border)
                {
                    Border border = (Border)element;
                    border.Child = null;
                }
                else if (element is Panel)
                {
                    Panel panel = (Panel)element;
                    panel.Children.Remove(button);
                }
            }
     
    Friday, October 31, 2008 5:39 AM
  • I think to get a UIElement's parent is quite simple, but when you get its parent, how could you remove it?

    Maybe switching the parent's type? It is quite a bad function. But I don't know what to do..

    Do you have some better method when get an element's parent as DependcyProperty?

    Friday, October 31, 2008 5:41 AM
  • Hi, IanBlackburn

    If the element's parent is popup? And if the element is just the content of a usercontrol?

    I think there may be more possibility to be considered. Is there a better method?

    Friday, October 31, 2008 5:46 AM
  • You can of course cast the Parent as a DependecyObject (not DependencyProperty) - but that does not have any Children or Child properties defined.  So that will not help you.

    So the method above is simply casting the UIElement (not "switching" not exactly sure what you mean here Wink ) to the correct type that defines the Children or Child property so you can do the remove.

    Friday, October 31, 2008 5:49 AM
  • With this Xaml:

     <Grid x:Name="LayoutRoot" Background="White">
            <StackPanel >
                <Button Content="Button1"></Button>
                <Button Content="Button2" Click="Button_Click"></Button>
            </StackPanel>
        </Grid>

     You could do this:

          private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                Panel element = button.Parent as Panel;
                element.Children.Remove(button);
            }

    This will work fine for things that derive from Panel: Grid, StackPanel, Canvas etc.

    If your element is in something else such as a Border which derives from UIElement and then defines it's own child property you would need to do this:

         private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                Border element = button.Parent as Border;
                element.Child = null;
            }


    So depending on how complex your xaml is you may need some conditional logic such as:

          private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                UIElement element = button.Parent as UIElement;
                if (element is Border)
                {
                    Border border = (Border)element;
                    border.Child = null;
                }
                else if (element is Panel)
                {
                    Panel panel = (Panel)element;
                    panel.Children.Remove(button);
                }
            }

     

    Thanks a lot.

    How to implement it in only Javascript?

    Friday, October 31, 2008 5:52 AM
  • Unfortunately, you will have to deal with each case independently because the Child and Children properties are not defined in a base class or Interface that you can cast to, they are define higher up the hierarchy.  So for you will need to just add other cases as they arise:

     

                Button button = (Button)sender;
                UIElement element = button.Parent as UIElement;
                if (element is Border )
                {
                    Border border = (Border)element;
                    border.Child = null;
                }
                else if (element is Panel)
                {
                    Panel panel = (Panel)element;
                    panel.Children.Remove(button);
                }
                else if (element is Popup)
                {
                    Popup panel = (Popup)element;
                    panel.Child = null;
                }

    The only alternative would be to use reflection to see if the object has a Child or Children property - performance is always hit when using relfection though, so I would not think it would be the best option here. 

    Friday, October 31, 2008 5:55 AM
  • With this Xaml:

     <Grid x:Name="LayoutRoot" Background="White">
            <StackPanel >
                <Button Content="Button1"></Button>
                <Button Content="Button2" Click="Button_Click"></Button>
            </StackPanel>
        </Grid>

     You could do this:

          private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                Panel element = button.Parent as Panel;
                element.Children.Remove(button);
            }

    This will work fine for things that derive from Panel: Grid, StackPanel, Canvas etc.

    If your element is in something else such as a Border which derives from UIElement and then defines it's own child property you would need to do this:

         private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                Border element = button.Parent as Border;
                element.Child = null;
            }


    So depending on how complex your xaml is you may need some conditional logic such as:

          private void Button_Click(object sender, RoutedEventArgs e)
            {
                Button button = (Button)sender;
                UIElement element = button.Parent as UIElement;
                if (element is Border)
                {
                    Border border = (Border)element;
                    border.Child = null;
                }
                else if (element is Panel)
                {
                    Panel panel = (Panel)element;
                    panel.Children.Remove(button);
                }
            }

     

    Thanks a lot.

    How to implement it in only Javascript?

     

    Here is an example.

    <Canvas x:Name="c1" ...>
      <Canvas x:Name="c2" ...>

        <Rectangle ... MouseLeftButtonDown="do"/>

        ......

      </Canvas>

      <Ellipse x:Name="e1" ... MouseLeftButtonDown="do" />
    </Canvas>

    Here you can say, there are many elements in the canvases named c1 and c2. I want to listen to the MouseLeftButtonDown event. Once the event is triggered I need to remove the element from the canvas. But the element may exists in c1 or c2.

    In the do function, I can get the name of the element. Now I need to remove it.

    That's why I ask this question.

    Friday, October 31, 2008 5:58 AM
  • How to implement it in only Javascript?

    Are you using Silvelright 1?  If so then the only container is the Canvas so the code will be simpler.  Or are you using SL 2 and the HtmlBridge?  Let me know which you are using and I'll post the sample code.

    Friday, October 31, 2008 5:58 AM
  • Hi, I'm using Silverlight 1. Thanks for your sample code in advance.

    By the way, could you explain the solution in Silverlight 2 and HtmlBridge?

    Friday, October 31, 2008 6:01 AM
  • Hi, I'm using Silverlight 1. Thanks for your sample code in advance.

     

    With this xaml

    <Canvas>
        <Rectangle x:Name="Rectangle1" Width="50" Height="50" Fill="Red"></Rectangle>
        <Rectangle Canvas.Top="100" x:Name="Rectangle2" Width="50" Height="50" Fill="Blue"></Rectangle>
        <Rectangle Canvas.Top="200"  x:Name="Rectangle3" Width="50" Height="50" Fill="Green"></Rectangle>
      </Canvas>


    You can use this JS:

    SilverlightRemoveElement.Scene.prototype =
    {
        handleLoad: function(plugIn, userContext, rootElement) {
            this.plugIn = plugIn;
    
            this.rect3 = rootElement.findName("Rectangle3");
            this.rect2 = rootElement.findName("Rectangle2");
            this.rect3.addEventListener("MouseLeftButtonUp", Silverlight.createDelegate(this, this.removeElement));
    
        },
    
        removeElement: function(sender, eventArgs) {
            var parent = this.rect2.GetParent();
            parent.Children.Remove(this.rect2);
        }
    }
     
    By the way, could you explain the solution in Silverlight 2 and HtmlBridge?
    The HtmlBridge is a way of having Silverlight 2 managed code talk to the Html Page (call JS method, maniuplate DOM Objects) or let javascript call managed code in the Silverlight object.
    More details here: http://silverlight.net/quickstarts/htmlbridge1.aspx
    Friday, October 31, 2008 6:22 AM
  • Hi, I'm using Silverlight 1. Thanks for your sample code in advance.

     

    With this xaml

    <Canvas>
        <Rectangle x:Name="Rectangle1" Width="50" Height="50" Fill="Red"></Rectangle>
        <Rectangle Canvas.Top="100" x:Name="Rectangle2" Width="50" Height="50" Fill="Blue"></Rectangle>
        <Rectangle Canvas.Top="200"  x:Name="Rectangle3" Width="50" Height="50" Fill="Green"></Rectangle>
      </Canvas>


    You can use this JS:

    SilverlightRemoveElement.Scene.prototype =
    {
        handleLoad: function(plugIn, userContext, rootElement) {
            this.plugIn = plugIn;
    
            this.rect3 = rootElement.findName("Rectangle3");
            this.rect2 = rootElement.findName("Rectangle2");
            this.rect3.addEventListener("MouseLeftButtonUp", Silverlight.createDelegate(this, this.removeElement));
    
        },
    
        removeElement: function(sender, eventArgs) {
            var parent = this.rect2.GetParent();
            parent.Children.Remove(this.rect2);
        }
    }
     
    By the way, could you explain the solution in Silverlight 2 and HtmlBridge?
    The HtmlBridge is a way of having Silverlight 2 managed code talk to the Html Page (call JS method, maniuplate DOM Objects) or let javascript call managed code in the Silverlight object.
    More details here: http://silverlight.net/quickstarts/htmlbridge1.aspx

    Thank you very much. Here I suffered from another problem.

    <Canvas Width="30" Height="40" Canvas.Left="42" Canvas.Top="83" x:Name="Piero" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" MouseLeftButtonDown="userLeftDown"><Canvas.Triggers><EventTrigger RoutedEvent="Canvas.Loaded">
     <BeginStoryboard>
      <Storyboard x:Name="GoalVideo0">
       <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Storyboard.TargetName="Piero" Storyboard.TargetProperty="(Canvas.Top)">

          <SplineDoubleKeyFrame KeyTime="00:00:00" Value="83"/>
       <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Storyboard.TargetName="Piero" Storyboard.TargetProperty="(Canvas.Left)">

          <SplineDoubleKeyFrame KeyTime="00:00:00" Value="42"/>
       </DoubleAnimationUsingKeyFrames>
      </Storyboard>
     </BeginStoryboard>
    </EventTrigger></Canvas.Triggers></Canvas>

    You can see in the example, there is one storyboard named GoalVideo0. Now I can just get the name, how can I remove it from the canvas by only Javascript?

    As the storyboard's parent is neither a canvas nor a InkPresenter.

    Thanks a lot.

    Sunday, November 02, 2008 11:25 PM
  • couple of points;

    1) The xaml seems to have a problem - you can't have a DoubleAnimationUsingKeyFrames nested inside another one.

    2) What is your objective here?  do you want to stop the animation playing?  I am not sure why you would want to remove this storyboard from the xaml.  To stop the animation just use :  this.goalVideo0.Stop();  Of course I may not have understood what your requirements are here, so please let me know if this is not appropiate.

    Monday, November 03, 2008 1:48 AM
  • Hi,

      My objective is that I need to create the animation dynamically. I mean that I need to create one animation for this element. Then I need to destroy the animation. At last one new animation may be created by the customer.

      I developed a tool to help customer build animations in the web page. I say, one ellipse E and two canvases A and B. Now E is in the canvas A. The customer creates one animation for E. Then he moved E into canvas B. If I do not remove the animation, once E is moved into B, the animation will be re-played. So I have to remove the storyboard object. Then one new animation could be built by the customer in canvas B.

      I hope you all understand my objective now.

      Do you have any idean on this case? Thanks

    Monday, November 03, 2008 3:20 AM
  • I see - sounds like a cool project!

    In your example your animation is added to the Triggers collection for the rootElement so you can use something like:

    this.rootElement.Triggers.Remove(this.myAnimation);

    This would remove the trigger for the animation but not the element it is animation on, nor would it stop the animation.  So stop the animation first, remove the element, then remove the trigger.

    Monday, November 03, 2008 3:46 AM
  • Great.

    Done.

    Thank you very much.

    Monday, November 03, 2008 4:11 AM